Zoom lens, projection display device, and imaging apparatus

ABSTRACT

The zoom lens includes: a first optical system on a magnification side; and a second optical system on a reduction side in a state where the intermediate image is formed between the magnification side and the reduction side. The first optical system includes, in order from the magnification side, a first-1 lens group which has a positive power, and a first-2 lens group which has a positive power. The second optical system includes, in order from the magnification side, a second-1 lens group which has a positive power, a second-2 lens group which has a positive power, and a second-3 lens group which has a positive power. The first-2 lens group, the second-1 lens group, and the second-2 lens group move during zooming. The first-1 lens group and the second-3 lens group remain stationary during zooming.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2016-168098 filed on Aug. 30, 2016. Theabove application is hereby expressly incorporated by reference, in itsentirety, into the present application.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a zoom lens forming an intermediateimage, a projection display device comprising the zoom lens, and animaging apparatus comprising the zoom lens.

2. Description of the Related Art

In the past, projection display devices, each of which uses a lightvalve such as a liquid crystal display element or a Digital MicromirrorDevice (DMD: registered trademark) display element, have come intowidespread use. In particular, some widely used devices adopt aconfiguration in which three light valves are used, illumination lightbeams with three primary colors of red, green, and blue respectivelycorrespond to the light valves, synthesizes the light beams, which aremodulated through the respective light valves, through a prism or thelike, and displays an image onto a screen through a zoom lens.

In such a zoom lens used in a type of the projection display device thatsynthesizes the light beams modulated through the three light valvesthrough a color synthesis optical system and projects the light beams,as described above, in order for a prism or the like for performingcolor synthesis to be disposed therein and in order to avoid a thermalproblem, a long back focal length is necessary. Further, since spectralcharacteristics of the color synthesizing prism change depending on anangle of incident light, it is necessary for the projection lens to havethe characteristic that the entrance pupil is at a sufficiently farposition in a case where the reduction side is set as the incident side,that is, to be telecentric on the reduction side.

It has become necessary for such a type of the zoom lens to performfavorable aberration correction appropriate for the resolutions of lightvalves. Further, from the viewpoint of installability, in order to copewith the demands to have a high zoom ratio function and to performprojection onto a large screen at a short distance, it is necessary fora zoom lens to have a wider angle of view.

A zoom lens, which forms an intermediate image at a position conjugateto the reduction side imaging plane and forms the intermediate imageagain on the magnification side imaging plane, has been proposed so asto cope with such demands (for example, JP2015-152890A).

SUMMARY OF THE INVENTION

In a normal zoom lens of a system which does not form an intermediateimage, in a case where an increase in angle of view is intended to beachieved by shortening a focal length thereof, the size of themagnification side lens inevitably becomes excessively large. However,in a zoom lens of a system which forms an intermediate image asdescribed above, it is possible to shorten a back focal length of thelens system closer to the magnification side than the intermediateimage. Therefore, it is possible to decrease a magnification side lensdiameter of the lens system closer to the magnification side than theintermediate image, and this configuration is appropriate for achievingan increase in angle of view by shortening a focal length thereof.However, fluctuation in aberrations becomes large during zooming, andthus a problem arises in that it is difficult to keep opticalperformance high in the entire zooming range.

In the lens system described in JP2015-152890A, there is also a problemthat fluctuation in aberrations is still large, and the zoom ratio isalso as low as about 1.3 times.

The present invention has been made in consideration of theabove-mentioned situation, and its object is to provide a zoom lens of asystem that forms an intermediate image and has high performance bysatisfactorily suppressing fluctuation in aberrations during zoomingwhile achieving a wide angle and a high zoom ratio, a projection displaydevice comprising the zoom lens, and an imaging apparatus comprising thezoom lens.

A zoom lens of the present invention forms an intermediate image at aposition conjugate to a reduction side imaging plane and forms theintermediate image again on a magnification side imaging plane. The zoomlens comprises: a first optical system on the magnification side; and asecond optical system on the reduction side. The intermediate image isformed between the magnification side and the reduction side. The firstoptical system includes, in order from the magnification side, a first-1lens group which has a positive refractive power, and a first-2 lensgroup which has a positive refractive power. The second optical systemincludes, in order from the magnification side, a second-1 lens groupwhich has a positive refractive power, a second-2 lens group which has apositive refractive power, and a second-3 lens group which has apositive refractive power. The first-2 lens group, the second-1 lensgroup, and the second-2 lens group are moved by changing spacingsbetween the groups adjacent to each other in a direction of an opticalaxis during zooming. In addition, the first-1 lens group and thesecond-3 lens group remain stationary with respect to the reduction sideimaging plane during zooming.

It is preferable that the zoom lens of the present invention satisfiesthe following conditional expression (1), and it is more preferable thatthe zoom lens satisfies the following conditional expression (1-1).5<f12/|fw|<20  (1)7<f12/|fw|<15  (1-1)

-   -   Here, f12 is a focal length of the first-2 lens group, and    -   fw is a focal length of the whole system at a wide-angle end.

It is preferable that the zoom lens satisfies the following conditionalexpression (2), and it is more preferable that the zoom lens satisfiesthe following conditional expression (2-1).5<f22/|fw|<12  (2)7<f22/|fw|<10  (2-1)

-   -   Here, f22 is a focal length of the second-2 lens group, and    -   fw is a focal length of the whole system at the wide-angle end.

It is preferable that the zoom lens satisfies the following conditionalexpression (3), and it is more preferable that the zoom lens satisfiesthe following conditional expression (3-1).5<f23/|fw|<12  (3)6.8<f23/|fw|<10  (3-1)

-   -   Here, f23 is a focal length of the second-3 lens group, and    -   fw is a focal length of the whole system at the wide-angle end.

It is preferable that, during zooming from the wide-angle end to atelephoto end, the second-1 lens group moves from the magnification sideto the reduction side, and the second-2 lens group moves from thereduction side to the magnification side.

It is preferable that the zoom lens satisfies the following conditionalexpression (4), and it is more preferable that the zoom lens satisfiesthe following conditional expression (4-1).−25<f211/|fw|<−2  (4)−20<f211/|fw|<−3  (4-1)

-   -   Here, f211 is a focal length of a lens closest to the        magnification side in the second-1 lens group, and    -   fw is a focal length of the whole system at the wide-angle end.

It is preferable that the lens closest to the magnification side in thesecond-1 lens group is a second-1-1 lens which has a negative refractivepower, a lens adjacent to the reduction side of the second-1-1 lens is asecond-1-2 lens which has a positive refractive power, and the zoom lenssatisfies the following conditional expression (5). In addition, it ismore preferable that the zoom lens satisfies the following conditionalexpression (5-1).30<ν211−ν212<70  (5)34<ν211−ν212<60  (5-1)

-   -   Here, ν211 is an Abbe number of the second-1-1 lens on the basis        of the d line, and    -   ν212 is an Abbe number of the second-1-2 lens on the basis of        the d line.

It is preferable that the zoom lens satisfies the following conditionalexpression (6), and it is more preferable that the zoom lens satisfiesthe following conditional expression (6-1).2<Bfw/|fw|  (6)3<Bfw/|fw|<10  (6-1)

-   -   Here, Bfw is a back focal length of the whole system as an air        conversion length at the wide-angle end, and    -   fw is a focal length of the whole system at the wide-angle end.

A projection display device of the present invention comprises: a lightsource; a light valve into which light originating from the light sourceis incident; and the zoom lens of the present invention, the zoom lensprojecting an optical image, which is formed by light modulated throughthe light valve, onto a screen.

An imaging apparatus of the present invention comprises theabove-mentioned zoom lens of the present invention.

It should be noted that the “magnification side” means a projected side(screen side). Even in a case where projection is performed in a reducedmanner, for convenience, the screen side is referred to as themagnification side. On the other hand, the “reduction side” means animage display element side (light valve side). Even in a case whereprojection is performed in a reduced manner, for convenience, the lightvalve side is referred to as the reduction side.

Further, the “comprises . . . or includes . . . ” means that the zoomlens may include not only the above-mentioned elements but also lensessubstantially having no powers, optical elements, which are not lenses,such as a mirror having no power, a stop, a mask, a cover glass, afilter, and the like.

Further, the “lens group” is not necessarily formed of a plurality oflenses, but may be formed of only one lens.

Further, regarding the “back focal length”, the following assumption isconsidered: the magnification side and the reduction side respectivelycorrespond to the object side and the image side of a general imaginglens, and the magnification side and the reduction side are respectivelyreferred to as the front side and the back side.

According to the present invention, the zoom lens forms an intermediateimage at the position conjugate to the reduction side imaging plane andforms the intermediate image again on the magnification side imagingplane. The zoom lens comprises: the first optical system on themagnification side; and the second optical system on the reduction side.The intermediate image is formed between the magnification side and thereduction side. The first optical system includes, in order from themagnification side, the first-1 lens group which has a positiverefractive power, and the first-2 lens group which has a positiverefractive power. The second optical system includes, in order from themagnification side, the second-1 lens group which has a positiverefractive power, the second-2 lens group which has a positiverefractive power, and the second-3 lens group which has a positiverefractive power. The first-2 lens group, the second-1 lens group, andthe second-2 lens group are moved by changing spacings between thegroups adjacent to each other in the direction of an optical axis duringzooming. In addition, the first-1 lens group and the second-3 lens groupremain stationary with respect to the reduction side imaging planeduring zooming. Therefore, it is possible to provide a zoom lens thathas high performance by satisfactorily suppressing fluctuation inaberrations during zooming while achieving a wide angle and a high zoomratio, a projection display device comprising the zoom lens, and animaging apparatus comprising the zoom lens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view illustrating a configuration of a zoomlens (common to Example 1) according to an embodiment of the presentinvention.

FIG. 2 is a cross-sectional view illustrating a configuration of a zoomlens of Example 2 of the present invention.

FIG. 3 is a cross-sectional view illustrating a configuration of a zoomlens of Example 3 of the present invention.

FIG. 4 is a diagram of aberrations of the zoom lens of Example 1 of thepresent invention.

FIG. 5 is a diagram of aberrations of the zoom lens of Example 2 of thepresent invention.

FIG. 6 is a diagram of aberrations of the zoom lens of Example 3 of thepresent invention.

FIG. 7 is a schematic configuration diagram of a projection displaydevice according to an embodiment of the present invention.

FIG. 8 is a schematic configuration diagram of a projection displaydevice according to another embodiment of the present invention.

FIG. 9 is a schematic configuration diagram of a projection displaydevice according to still another embodiment of the present invention.

FIG. 10 is a perspective view of the front side of an imaging apparatusaccording to an embodiment of the present invention.

FIG. 11 is a perspective view of the rear side of the imaging apparatusshown in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described withreference to drawings. FIG. 1 is a cross-sectional view illustrating aconfiguration of a zoom lens according to an embodiment of the presentinvention. The exemplary configuration shown in FIG. 1 is the same asthe configuration of the zoom lens of Examples 1 to be described later.FIG. 1 shows a state at the wide-angle end, where an image displaysurface Sim side is the reduction side, a lens L11 a side of the firstoptical system G1 is a magnification side, and an aperture stop St shownin the drawing does not necessarily show its real size and shape, butshow a position on an optical axis Z. Further, in FIG. 1, on-axis rayswa and rays with a maximum angle of view wb are also shown together.

This zoom lens is, for example, mounted on a projection display device,and can be used to project image information displayed on the lightvalve onto the screen. In FIG. 1, assuming that the zoom lens is mountedon the projection display device, an optical member PP such as a filteror a prism used in a color synthesizing section or an illumination lightseparating section, and an image display surface Sim of a light valvepositioned on a reduction side surface of the optical member PP are alsoshown. In the projection display device, rays, which are made to haveimage information through the image display surface Sim on the imagedisplay element, are incident into the zoom lens through the opticalmember PP, and are transmitted onto a screen, which is not shown in thedrawing, through the zoom lens.

As shown in FIG. 1, a zoom lens of the present embodiment forms anintermediate image I at a position conjugate to a reduction side imagingplane (image display surface Sim) and forms the intermediate image againon a magnification side imaging plane. The zoom lens includes: a firstoptical system G1 on the magnification side; and a second optical systemG2 on the reduction side. The intermediate image is formed therebetween.The first optical system G1 includes, in order from the magnificationside, a first-1 lens group G11 which has a positive refractive power,and a first-2 lens group G12 which has a positive refractive power. Thesecond optical system G2 includes, in order from the magnification side,a second-1 lens group G21 which has a positive refractive power, asecond-2 lens group G22 which has a positive refractive power, and asecond-3 lens group G23 which has a positive refractive power. Thefirst-2 lens group G12, the second-1 lens group G21, and the second-2lens group G22 are moved by changing spacings between the groupsadjacent to each other in a direction of an optical axis during zooming.In addition, the first-1 lens group G11 and the second-3 lens group G23remain stationary with respect to the reduction side imaging planeduring zooming.

In a normal zoom lens of a system which does not form an intermediateimage, in a case where an increase in angle of view is intended to beachieved by shortening a focal length thereof, the size of themagnification side lens inevitably becomes excessively large. However,in a manner similar to that of the present embodiment, in a zoom lens ofa system which forms an intermediate image, it is possible to shorten aback focal length of the lens system (in the example shown in FIG. 1,the first optical system G1) closer to the magnification side than theintermediate image. In addition, it is possible to decrease amagnification side lens diameter, and this configuration is appropriatefor achieving an increase in angle of view by shortening a focal lengththereof.

Further, zooming is performed by moving a lens system closer to thereduction side than the intermediate image. As for the zoomingoperation, change in relay magnification of the lens system closer tothe reduction side than the intermediate image corresponds to change insize of the intermediate image, and thus it is possible to achieve anoptically simple configuration. However, in a case where the zoom ratiois intended to be increased by using only the lens system closer to thereduction side than the intermediate image, the change in relaymagnification, that is, the change in size of the intermediate imagebecomes large. Therefore, this causes an increase in magnification sidelens diameter in the lens system closer to the reduction side than theintermediate image. Further, in only the lens system closer to thereduction side than the intermediate image, zooming is performed withoutchange in position of the intermediate image. Thus, a problem arises inthat spherical aberration at the telephoto end becomes large due to anincrease in zoom ratio.

Accordingly, during zooming, by moving not only the second-1 lens groupG21 and the second-2 lens group G22 closer to the reduction side thanthe intermediate image but also the first-2 lens group G12 closer to themagnification side than the intermediate image, it is possible to acorrection operation for suppressing the increase in sphericalaberration at the telephoto end while providing the zooming operationaccompanied with the increase in magnification. In addition, it ispossible to reduce fluctuation in aberrations during zooming whilemaintaining favorable telecentricity in the entire zooming range.

Further, the second-3 lens group G23, which remains stationary withrespect to the reduction side imaging plane during zooming and has apositive refractive power, is disposed to be closest to the reductionside. Thereby, it is possible to reduce fluctuation in aberrationsduring zooming while maintaining telecentricity.

It is preferable that the zoom lens of the present invention satisfiesthe following conditional expression (1). By not allowing the result ofthe conditional expressions (1) to be equal to or less than the lowerlimit, the power of the first-2 lens group G12 can be prevented frombecoming excessively strong. Thus, an incident angle of rays enteringinto the second optical system G2 does not become excessively oblique toan optical axis Z. As a result, it becomes easy not only to ensure azoom ratio, but also to perform aberration correction in the whole lenssystem. By not allowing the result of the conditional expressions (1) tobe equal to or greater than the upper limit, the power of the first-2lens group G12 can be prevented from becoming excessively weak. Thus, itis possible to appropriately correct spherical aberration even at thetelephoto end. In addition, in a case where the following conditionalexpression (1-1) is satisfied, it is possible to obtain more favorablecharacteristics.5<f12/|fw|<20  (1)7<f12/|fw|<15  (1-1)

-   -   Here, f12 is a focal length of the first-2 lens group G12, and    -   fw is a focal length of the whole system at the wide-angle end.

It is preferable that the zoom lens satisfies the following conditionalexpression (2). By not allowing the result of the conditional expression(2) to be equal to or less than the lower limit, the power of thesecond-2 lens group G22 can be prevented from becoming excessivelystrong. Thus, it is possible to suppress fluctuation in longitudinalchromatic aberration and spherical aberration during zooming. By notallowing the result of the conditional expression (2) to be equal to orgreater than the upper limit, the power of the second-2 lens group G22can be prevented from becoming excessively weak. Thus, an amount ofmovement for ensuring the desired zoom ratio is minimized, and thiscontributes to reduction in lens total length. In addition, in a casewhere the following conditional expression (2-1) is satisfied, it ispossible to obtain more favorable characteristics.5<f22/|fw|<12  (2)7<f22/|fw|<10  (2-1)

-   -   Here, f22 is a focal length of the second-2 lens group G22, and    -   fw is a focal length of the whole system at the wide-angle end.

It is preferable that the zoom lens satisfies the following conditionalexpression (3). By not allowing the result of the conditional expression(3) to be equal to or less than the lower limit, the power of thesecond-3 lens group G23 can be prevented from becoming excessivelystrong. Thus, by minimizing an amount of occurrence of lateral chromaticaberration, it is possible to easily correct lateral chromaticaberration in other groups. By not allowing the result of theconditional expression (3) to be equal to or greater than the upperlimit, the power of the second-3 lens group G23 can be prevented frombecoming excessively weak. Thus, it becomes easy to attain a state wherethe zoom lens is telecentric on the reduction side. In addition, in acase where the following conditional expression (3-1) is satisfied, itis possible to obtain more favorable characteristics.5<f23/|fw|<12  (3)6.8<f23/|fw|<10  (3-1)

-   -   Here, f23 is a focal length of the second-3 lens group G23, and    -   fw is a focal length of the whole system at the wide-angle end.

It is preferable that, during zooming from the wide-angle end to atelephoto end, the second-1 lens group G21 moves from the magnificationside to the reduction side, and the second-2 lens group G22 moves fromthe reduction side to the magnification side. With such a configuration,it is possible to reduce fluctuation in aberrations during zooming.

It is preferable that the zoom lens satisfies the following conditionalexpression (4). By not allowing the result of the conditional expression(4) to be equal to or less than the lower limit, the power of the lensclosest to the magnification side L21 a in the second-1 lens group G21can be prevented from becoming excessively weak. Thus, it becomes easyto correct distortion. By not allowing the result of the conditionalexpression (4) to be equal to or greater than the upper limit, the powerof the lens closest to the magnification side L21 a in the second-1 lensgroup G21 can be prevented from becoming excessively strong. Thus, theforce of deflecting rays toward the outside becomes weak, and it ispossible to prevent the lens diameter and the lens total length of thesubsequent (reduction side) lens from being increased. In addition, in acase where the following conditional expression (4-1) is satisfied, itis possible to obtain more favorable characteristics.−25<f211/|fw|<−2  (4)−20<f211/|fw|<−3  (4-1)

-   -   Here, f211 is a focal length of a lens closest to the        magnification side in the second-1 lens group G21, and    -   fw is a focal length of the whole system at the wide-angle end.

It is preferable that the lens closest to the magnification side in thesecond-1 lens group G21 is a second-1-1 lens L21 a which has a negativerefractive power, a lens adjacent to the reduction side of thesecond-1-1 lens L21 a is a second-1-2 lens L21 b which has a positiverefractive power, and the zoom lens satisfies the following conditionalexpression (5). By not allowing the result of the conditional expression(5) to be equal to or less than the lower limit, it is possible toprevent a difference in Abbe number between the second-1-1 lens L21 awhich has a negative refractive power and the second-1-2 lens L21 bwhich has a positive refractive power. Therefore, it is possible toappropriately correct longitudinal chromatic aberration in the twolenses. As a result, it does not become necessary to excessivelyincrease the number of lenses in the second-1 lens group G21. By notallowing the result of the conditional expression (5) to be equal to orgreater than the upper limit, expensive glass materials do not becomenecessary for the second-1-1 lens L21 a which has a negative refractivepower and the second-1-2 lens L21 b which has a positive refractivepower. As a result, it is possible to prevent costs thereof from beingincreased. In addition, in a case where the following conditionalexpression (5-1) is satisfied, it is possible to obtain more favorablecharacteristics.30<ν211−ν212<70  (5)34<ν211−ν212<60  (5-1)

-   -   Here, ν211 is an Abbe number of the second-1-1 lens L21 a on the        basis of the d line, and    -   ν212 is an Abbe number of the second-1-2 lens L21 b on the basis        of the d line.

It is preferable that the zoom lens satisfies the following conditionalexpression (6). By not allowing the result of the conditional expression(6) to be equal to or less than the lower limit, it is possible toprevent the back focal length from being excessively shortened. Thus, itbecomes easy to arrange the color synthesizing prism and the like. Inaddition, in a case where the following conditional expression (6-1) issatisfied, it is possible to obtain more favorable characteristics. Bynot allowing the result of the conditional expression (6-1) to be equalto or greater than the upper limit, it is possible to prevent the backfocal length from becoming excessively large and the lens diameter frombecoming large. Thus, it is possible to suppress an increase in numberof lenses and an increase in costs of materials.2<Bfw/|fw|  (6)3<Bfw/|fw|<10  (6-1)

-   -   Here, Bfw is a back focal length of the whole system as an air        conversion length at the wide-angle end, and    -   fw is a focal length of the whole system at the wide-angle end.

Next, numerical examples of the zoom lens of the present invention willbe described.

-   -   First, a zoom lens of Example 1 will be described. FIG. 1 is a        cross-sectional diagram illustrating a configuration of the zoom        lens of Example 1. In addition, in FIG. 1 and FIGS. 2 and 3        corresponding to Examples 2 and 3 to be described later, an        image display surface Sim side is the reduction side, and a lens        L11 a side of the first optical system G1 is a magnification        side, an aperture stop St shown in the drawing does not        necessarily show its real size and shape, but show a position on        the optical axis Z. Further, in FIGS. 1 to 3, on-axis rays wa        and rays with a maximum angle of view wb are also shown        together.

The zoom lens of Example 1 includes a first optical system G1 on themagnification side, and a second optical system G2 on the reductionside, in a state where the intermediate image is formed therebetween.The first optical system G1 includes a first-1 lens group G11 and afirst-2 lens group G12. The second optical system G2 includes a second-1lens group G21, a second-2 lens group G22, and a second-3 lens groupG23.

The first-2 lens group G12, the second-1 lens group G21, and thesecond-2 lens group G22 are moved by changing spacings between thegroups adjacent to each other in a direction of an optical axis duringzooming. In addition, the first-1 lens group G11 and the second-3 lensgroup G23 remain stationary with respect to the reduction side imagingplane during zooming.

The first-1 lens group G11 includes nine lenses as lenses L11 a to L11i. The first-2 lens group G12 includes two lenses as lenses L12 a andL12 b. The second-1 lens group G21 includes four lenses as lenses L21 ato L21 d. The second-2 lens group G22 includes six lenses as lenses L22a to L22 f. The second-3 lens group G23 includes one lens as only a lensL23 a.

Table 1 shows lens data of the zoom lens of Example 1, Table 2 showsdata about specification, Table 3 shows surface spacings which arevariable during zooming, and Table 4 shows data about asphericcoefficients thereof. Hereinafter, meanings of the reference signs inthe tables are, for example, as described in Example 1, and arebasically the same as those in Examples 2 and 3.

In the lens data of Table 1, the column of the surface number showssurface numbers. The surface of the elements closest to themagnification side is the first surface, and the surface numberssequentially increase toward the reduction side. The column of theradius of curvature shows radii of curvature of the respective surfaces.The column of the on-axis surface spacing shows spacings on the opticalaxis Z between the respective surfaces and the subsequent surfaces.Further, the column of n shows a refractive index of each opticalelement at the d line (a wavelength of 587.6 nm), and the column of νshows an Abbe number of each optical element at the d line (a wavelengthof 587.6 nm). Here, the sign of the radius of curvature is positive in acase where a surface has a shape convex toward the magnification side,and is negative in a case where a surface has a shape convex toward thereduction side. In the lens data, the aperture stop St and the opticalmember PP are additionally noted. In a place of a surface number of asurface corresponding to the aperture stop St, the surface number and aterm of (stop) are noted. Further, in the lens data, in each place ofthe surface spacing which is variable during zooming, DD[surface number]is noted. Numerical values each corresponding to the DD[surface number]are shown in Table 3.

In the data about the specification of Table 2, values of the zoomratio, the focal length f′, the F number FNo., and the total angle ofview 2ω are noted.

In the lens data of Table 1, the reference sign * is attached to surfacenumbers of aspheric surfaces, and radii of curvature of the asphericsurfaces are represented by numerical values of paraxial radii ofcurvature. In the data about aspheric coefficients of Table 4, surfacenumbers of aspheric surfaces, and aspheric coefficients of theseaspheric surfaces are noted. The “E±n” (n: an integer) in numericalvalues of the aspheric coefficients of Table 4 indicates “×10^(±n)”. Theaspheric coefficients are values of the coefficients KA and Am (m=3 . .. 20) in aspheric surface expression represented by the followingexpression.Zd=C·h ²/{1+(1−KA·C ² ·h ²)^(1/2) }+ΣAm·h ^(m)

-   -   Here, Zd is an aspheric surface depth (a length of a        perpendicular from a point on an aspheric surface at height h to        a plane that is perpendicular to the optical axis and contacts        with the vertex of the aspheric surface),    -   h is a height (a distance from the optical axis),    -   C is an inverse of a paraxial radius of curvature, and    -   KA and Am are aspheric coefficients (m=3 . . . 20).

TABLE 1 EXAMPLE 1 • LENS DATA (n AND ν ARE BASED ON d LINE) SURFACERADIUS OF SURFACE NUMBER CURVATURE SPACING n ν  *1 −15.3257 3.10411.53158 55.08  *2 −33.1892 10.0852  3 40.4538 2.4685 1.62041 60.29  48.6430 10.0936  5 −11.2762 7.2577 1.83481 42.72  6 −17.0955 0.1381  7182.9952 2.4765 1.89286 20.36  8 −36.5411 2.0001  9 35.6081 0.93171.75520 27.51  10 16.8209 6.8261 1.49700 81.61  11 −25.4795 0.3399  12267.6247 0.9304 1.84666 23.78  13 18.9387 6.7530 1.49700 81.61  14−42.8291 0.1383 *15 106.4754 2.6191 1.49100 57.58 *16 −349.9175 DD[16] 17 30.8964 7.7906 1.80400 46.58  18 −83.2641 2.7908  19 −35.5354 1.03451.54814 45.78  20 74.1099 DD[20]  21 −50.1018 1.2416 1.48749 70.24  2267.5112 2.4368  23 445.9501 7.6268 1.80518 25.42  24 −35.0369 1.0354  2528.9876 11.7241 1.80100 34.97  26 −37.3021 1.3867 1.78472 25.68  2724.2172 DD[27]  28 40.2271 3.4845 1.80610 40.93  29 −134.3021 6.4061  3014.8879 3.2023 1.59282 68.62  31 40.2390 0.8342 1.51742 52.43  3210.6429 3.4847  33 (STOP) ∞ 4.7459  34 −14.0751 5.7552 1.85478 24.80  35121.0700 3.5097 1.59282 68.62  36 −20.9375 0.1385  37 53.7339 4.47321.43875 94.66  38 −23.5498 DD[38]  39 32.9929 3.7045 1.80809 22.76  40286.0748 9.1738  41 ∞ 22.2759 1.51633 64.14  42 ∞

TABLE 2 EXAMPLE 1 • SPECIFICATION (d LINE) WIDE-ANGLE END TELEPHOTO ENDZOOM 1.0 1.6 RATIO f′ −5.71 −9.14 FNo. 2.00 2.32 2ω [°] 120.4 95.4

TABLE 3 EXAMPLE 1 • SURFACE SPACING WIDE-ANGLE END TELEPHOTO END DD[16]14.3660 18.1309 DD[20] 22.1353 27.6169 DD[27] 30.2604 4.8273 DD[38]14.1661 30.3527

TABLE 4 EXAMPLE 1 • ASPHERIC COEFFICIENT SURFACE NUMBER 1 2 15 KA2.4141499E−01 1.2443569E+00 1.0000000E+00 A3 −1.0548641E−03−8.8448311E−04 9.9188567E−05 A4 8.3674285E−04 6.3492583E−043.0661548E−05 A5 −6.2203974E−05 −2.5148517E−05 4.3824644E−05 A6−1.6931733E−06 −4.7634497E−06 −1.4133218E−05 A7 4.3265443E−074.6820320E−07 1.7507446E−06 A8 −9.2963393E−09 7.7190760E−101.6107809E−07 A9 −1.4486672E−09 −1.7808022E−09 −6.5380545E−08 A107.8786293E−11 4.9251890E−11 2.8124535E−09 A11 1.7996418E−123.5072008E−12 8.8411414E−10 A12 −2.2614666E−13 −2.0320674E−13−1.0033635E−10 A13 1.6945437E−15 −1.2839303E−15 −3.1296368E−12 A143.0897395E−16 3.2125472E−16 9.9989872E−13 A15 −7.5571704E−18−4.7675296E−18 −2.7219117E−14 A16 −1.7512626E−19 −2.3371888E−19−3.9426279E−15 A17 8.0909075E−21 8.0064105E−21 2.5945002E−16 A18−9.3635563E−24 9.2687753E−24 2.3858327E−18 A19 −2.9829776E−24−3.5001412E−24 −6.0714673E−19 A20 3.4190869E−26 4.0836144E−261.4353112E−20 SURFACE NUMBER 16 KA 1.0000000E+00 A3 −1.9710878E−04 A42.7699157E−04 A5 −3.4909821E−05 A6 5.8330314E−07 A7 1.2714550E−06 A8−1.8605027E−07 A9 −5.4440996E−09 A10 2.8459871E−09 A11 −9.8577866E−11A12 −1.9648267E−11 A13 1.5012748E−12 A14 5.0112842E−14 A15−8.7059294E−15 A16 1.2726604E−16 A17 2.3563163E−17 A18 −1.0153859E−18A19 −2.4244280E−20 A20 1.6658139E−21

FIG. 4 shows aberration diagrams of the zoom lens of Example 1. Inaddition, in order from the upper left side of FIG. 4, sphericalaberration, astigmatism, distortion, and lateral chromatic aberration atthe wide-angle end are shown. In order from the lower left side of FIG.4, spherical aberration, astigmatism, distortion, and lateral chromaticaberration at the telephoto end are shown. These aberration diagramsshow states in a case where the projection distance is set as distancesnoted in the aberration diagrams. The aberration diagrams illustratingspherical aberration, astigmatism, and distortion indicate aberrationsthat occur in a case where the d line (a wavelength of 587.6 nm) is setas a reference wavelength. In the spherical aberration diagram,aberrations at the d line (a wavelength of 587.6 nm), the C line (awavelength of 656.3 nm), and the F line (a wavelength of 486.1 nm) arerespectively indicated by the solid line, the long dashed line, and theshort dashed line. In the astigmatism diagram, aberrations in sagittaland tangential directions are respectively indicated by the solid lineand the short dashed line. In the lateral chromatic aberration,aberrations at the C line (wavelength 656.3 nm) and F line (wavelength486.1 nm) are respectively indicated by the long dashed line and theshort dashed line. In the spherical aberration diagram, FNo. means an Fnumber. In the other aberration diagrams, ω means a half angle of view.

Reference signs, meanings, and description methods of the respectivedata pieces according to Example 1 described above are the same as thosein the following examples unless otherwise noted. Therefore, in thefollowing description, repeated description will be omitted.

Next, a zoom lens of Example 2 will be described. FIG. 2 is across-sectional diagram illustrating a configuration of the zoom lens ofExample 2. The zoom lens of Example 2 has the same lens groups and hasthe same number of lenses as that of Example 1 except that the second-2lens group G22 includes five lenses as the lenses L22 a to L22 e. Table5 shows lens data of the zoom lens of Example 2, Table 6 shows dataabout specification, Table 7 shows surface spacings which are variableduring zooming, Table 8 shows data about aspheric coefficients thereof,and FIG. 5 shows aberration diagrams.

TABLE 5 EXAMPLE 2 • LENS DATA (n AND ν ARE BASED ON d LINE) SURFACERADIUS OF SURFACE NUMBER CURVATURE SPACING n ν  *1 −15.3257 3.10371.53158 55.08  *2 −34.7664 11.4247  3 40.3127 1.7647 1.62299 58.16  48.3917 9.8338  5 −10.9413 7.9941 1.83481 42.72  6 −16.9770 0.1377  7188.6544 2.5038 1.89286 20.36  8 −38.7881 1.9933  9 34.2031 0.94601.72825 28.46  10 16.8209 7.2415 1.49700 81.61  11 −26.7371 0.5298  12349.2887 0.9309 1.84666 23.78  13 18.5093 7.1110 1.49700 81.61  14−41.7340 0.1386 *15 79.5713 2.7662 1.49100 57.58 *16 −621.3076 DD[16] 17 29.6563 7.5688 1.80400 46.58  18 −95.4511 2.5605  19 −36.6865 1.03391.51742 52.43  20 44.0816 DD[20]  21 −51.4439 1.2418 1.48749 70.24  2269.7223 2.2483  23 441.0518 7.4804 1.80518 25.42  24 −34.1355 1.6469  2528.8569 11.7241 1.80100 34.97  26 −33.2020 1.5448 1.78472 25.68  2724.1607 DD[27]  28 33.6046 3.5630 1.80100 34.97  29 −180.2001 8.5971  3013.5482 1.2464 1.51742 52.43  31 10.9987 3.2101  32 (STOP) ∞ 3.4919  33−14.0473 4.4740 1.85478 24.80  34 70.6017 3.6976 1.59282 68.62  35−20.0695 0.1380  36 48.5692 4.7586 1.43875 94.66  37 −23.3893 DD[37]  3835.4283 3.8641 1.80809 22.76  39 ∞ 9.1746  40 ∞ 22.2759 1.51633 64.14 41 ∞

TABLE 6 EXAMPLE 2 • SPECIFICATION (d LINE) WIDE-ANGLE END TELEPHOTO ENDZOOM 1.0 1.5 RATIO f′ −5.71 −8.57 FNo. 2.00 2.27 2ω [°] 120.4 98.8

TABLE 7 EXAMPLE 2 • SURFACE SPACING WIDE-ANGLE END TELEPHOTO END DD[16]16.5809 19.4606 DD[20] 20.2889 25.0617 DD[27] 27.0637 5.4902 DD[37]17.4423 31.3634

TABLE 8 EXAMPLE 2 • ASPHERIC COEFFICIENT SURFACE NUMBER 1 2 15 KA2.4005572E−01 1.2982535E+00 1.0000000E+00 A3 −9.4117956E−04−8.1119456E−04 8.4641293E−05 A4 8.2140376E−04 6.3727543E−046.0083889E−05 A5 −6.1338797E−05 −2.7193363E−05 1.6551479E−05 A6−1.6412446E−06 −4.5371150E−06 −7.5231031E−06 A7 4.2425029E−074.9118627E−07 1.5936698E−06 A8 −9.2480460E−09 −4.2465019E−09−4.8437602E−08 A9 −1.4192032E−09 −1.7105698E−09 −3.6848452E−08 A107.8161464E−11 7.7499087E−11 4.6263308E−09 A11 1.7400643E−122.3931525E−12 2.9213247E−10 A12 −2.2454204E−13 −2.8190216E−13−8.8147072E−11 A13 1.7770892E−15 3.5062529E−15 2.0337483E−12 A143.0669185E−16 4.1255051E−16 6.9640960E−13 A15 −7.6406657E−18−1.4330874E−17 −4.6551873E−14 A16 −1.7295229E−19 −2.3154553E−19−2.0436648E−15 A17 8.1462036E−21 1.7632132E−20 2.7187232E−16 A18−1.0736468E−23 −9.6081658E−23 −1.9938241E−18 A19 −2.9999139E−24−7.2952143E−24 −5.4287538E−19 A20 3.4610499E−26 1.0689391E−251.5952204E−20 SURFACE NUMBER 16 KA 1.0000000E+00 A3 −1.1528411E−04 A42.3260739E−04 A5 −3.3901237E−05 A6 1.9336831E−06 A7 1.2051151E−06 A8−2.5129854E−07 A9 1.4573787E−09 A10 4.2460303E−09 A11 −3.1764927E−10 A12−3.1421344E−11 A13 4.6018352E−12 A14 5.3879028E−14 A15 −3.0930304E−14A16 6.6051246E−16 A17 1.0269513E−16 A18 −4.0507934E−18 A19−1.3563390E−19 A20 6.9559387E−21

Next, a zoom lens of Example 3 will be described. FIG. 3 is across-sectional diagram illustrating a configuration of the zoom lens ofExample 3. The zoom lens of Example 3 has the same lens groups and hasthe same number of lenses as that of Example 1 except that the first-1lens group G11 includes ten lenses as the lenses L11 a to L11 j. Table 9shows lens data of the zoom lens of Example 3, Table 10 shows data aboutspecification, Table 11 shows surface spacings which are variable duringzooming, Table 12 shows data about aspheric coefficients thereof, andFIG. 6 shows aberration diagrams.

TABLE 9 EXAMPLE 3 • LENS DATA (n AND ν ARE BASED ON d LINE) SURFACERADIUS OF SURFACE NUMBER CURVATURE SPACING n ν  *1 −15.3257 3.10281.53158 55.08  *2 −31.6988 5.2042  3 30.9863 1.1727 1.58913 61.13  413.6578 3.9397  5 28.3329 1.0341 1.51633 64.14  6 8.9464 10.7839  7−11.1233 5.4675 1.83481 42.72  8 −15.5265 0.1372  9 143.1892 3.69441.89286 20.36  10 −37.1115 3.0805  11 31.3949 0.9315 1.80518 25.42  1216.8208 6.9787 1.43700 95.10  13 −21.4677 0.1380  14 84.7476 0.93041.84666 23.78  15 16.8209 7.0661 1.53775 74.70  16 −52.6740 0.1386 *17−58.3536 2.6207 1.49100 57.58 *18 −35.5498 DD[18]  19 32.7044 8.06871.80400 46.58  20 −79.2698 2.4029  21 −38.0466 1.0348 1.80400 46.58  22−1333.1627 DD[22]  23 −66.0194 1.2407 1.51633 64.14  24 64.3595 2.2877 25 201.8116 7.8561 1.80518 25.42  26 −39.7236 0.1384  27 27.484911.7312 1.80100 34.97  28 −48.0253 2.7581 1.80518 25.42  29 22.2474DD[29]  30 44.3155 3.2562 1.80400 46.58  31 −104.7801 6.0852  32 15.12823.2596 1.59282 68.62  33 59.6249 0.8282 1.51742 52.43  34 10.7044 3.4560 35 (STOP) ∞ 5.2553  36 −13.3432 3.6321 1.85478 24.80  37 −5957.11463.7438 1.53775 74.70  38 −17.0898 1.8040  39 64.5953 4.9353 1.4370095.10  40 −22.4833 DD[40]  41 32.5054 3.7499 1.80809 22.76  42 220.88639.1701  43 ∞ 22.2759 1.51633 64.14  44 ∞

TABLE 10 EXAMPLE 3 • SPECIFICATION (d LINE) WIDE-ANGLE END TELEPHOTO ENDZOOM 1.0 1.6 RATIO f′ −4.81 −7.70 FNo. 2.00 2.32 2ω [°] 128.4 104.8

TABLE 11 EXAMPLE 3 • SURFACE SPACING WIDE-ANGLE END TELEPHOTO END DD[18]14.9185 18.3610 DD[22] 24.4207 29.7437 DD[29] 29.6253 4.8276 DD[40]11.0084 27.0407

TABLE 12 EXAMPLE 3 • ASPHERIC COEFFICIENT SURFACE NUMBER 1 2 17 KA2.4117736E−01 1.1608014E+00 1.0000000E+00 A3 −1.6271941E−03−1.2767832E−03 4.6160698E−05 A4 9.2393927E−04 6.4814859E−041.5700729E−04 A5 −6.4865923E−05 −1.8308130E−05 −9.8767281E−06 A6−2.0953765E−06 −5.1769760E−06 −1.8540436E−06 A7 4.6370052E−073.8215770E−07 1.5724419E−06 A8 −8.8835584E−09 9.3455161E−09−2.4267871E−07 A9 −1.5529544E−09 −1.5866351E−09 −1.3005679E−08 A108.0307856E−11 3.1715243E−12 6.3587257E−09 A11 1.9639440E−123.9344927E−12 −2.7272261E−10 A12 −2.3087125E−13 −7.2745777E−14−6.6948599E−11 A13 1.5610063E−15 −5.0832636E−15 6.4982988E−12 A143.1391634E−16 1.4714489E−16 2.6061654E−13 A15 −7.4711657E−183.6785163E−18 −5.2614420E−14 A16 −1.7755804E−19 −1.5073768E−193.9616799E−16 A17 8.0091867E−21 −7.8628119E−22 1.9339609E−16 A18−8.0613382E−24 6.3296481E−23 −5.6822445E−18 A19 −2.9400840E−24−8.8820438E−26 −2.7192341E−19 A20 3.3436139E−26 −8.5354333E−271.1491509E−20 SURFACE NUMBER 18 KA 1.0000000E+00 A3 7.5227206E−05 A41.9942153E−04 A5 −2.2308171E−05 A6 3.8844805E−06 A7 4.3203997E−07 A8−2.0578667E−07 A9 1.4354863E−08 A10 2.1761088E−09 A11 −3.5226020E−10 A12−3.9084914E−12 A13 3.3735385E−12 A14 −1.0163967E−13 A15 −1.6498532E−14A16 8.9330756E−16 A17 4.0082629E−17 A18 −2.9907569E−18 A19−3.7359448E−20 A20 3.7092475E−21

Table 13 shows values corresponding to the conditional expressions (1)to (6) of the zoom lenses of Examples 1 to 3. It should be noted that,in the above-mentioned examples, the d line is set as the referencewavelength, and the values shown in the following Table 13 are values atthe reference wavelength.

TABLE 13 EXPRESSION CONDITIONAL EXAM- EXAM- NUMBER EXPRESSION PLE 1EXAMPLE 2 PLE 3 (1) f12/|fw| 10.51 12.37 12.22 (2) f22/|fw| 8.26 8.139.75 (3) f23/|fw| 8.03 7.67 9.71 (4) f211/|fw| −10.29 −10.59 −13.07 (5)ν211 − ν212 44.81 44.81 38.71 (6) Bfw/|fw| 4.17 4.17 4.95

As can be seen from the above-mentioned data, each of the zoom lenses ofExamples 1 to 3 is a zoom lens of the system that satisfies conditionalexpressions (1) to (6) and forms an intermediate image, and is a zoomlens that has an F number as bright as 2.3 or less, has a total angle ofview as a wide angle of 110° or more, has a zoom ratio as high as 1.4times, and has high performance by satisfactorily suppressingfluctuation in aberrations during zooming.

Next, a projection display device according to an embodiment of thepresent invention will be described. FIG. 7 is a schematic configurationdiagram of the projection display device according to the embodiment ofthe present invention. The projection display device 100 shown in FIG. 7has a zoom lens 10 according to the embodiment of the present invention,a light source 15, transmissive display elements 11 a to 11 c as lightvalves corresponding to respective color light beams, dichroic mirrors12 and 13 for color separation, a cross dichroic prism 14 for colorsynthesis, condenser lenses 16 a to 16 c, and total reflection mirrors18 a to 18 c for deflecting the optical path. In FIG. 7, the zoom lens10 is schematically illustrated. Further, an integrator is disposedbetween the light source 15 and the dichroic mirror 12, but illustrationthereof is omitted in FIG. 7.

White light originating from the light source 15 is separated into rayswith three colors (G light, B light, R light) through the dichroicmirrors 12 and 13. Thereafter, the rays respectively pass through thecondenser lenses 16 a to 16 c, are incident into and modulated throughthe transmissive display elements 11 a to 11 c respectivelycorresponding to the rays with the respective colors, are subjected tocolor synthesis through the cross dichroic prism 14, and aresubsequently incident into the zoom lens 10. The zoom lens 10 projectsan optical image, which is formed by the light modulated through thetransmissive display elements 11 a to 11 c, onto a screen 105.

FIG. 8 is a schematic configuration diagram of a projection displaydevice according to another embodiment of the present invention. Theprojection display device 200 shown in FIG. 8 has a zoom lens 210according to the embodiment of the present invention, a light source215, DMD elements 21 a to 21 c as light valves corresponding torespective color light beams, total internal reflection (TIR) prisms 24a to 24 c for color separation and color synthesis, and a polarizationseparating prism 25 that separates illumination light and projectionlight. In FIG. 8, the zoom lens 210 is schematically illustrated.Further, an integrator is disposed between the light source 215 and thepolarization separating prism 25, but illustration thereof is omitted inFIG. 8.

White light originating from the light source 215 is reflected on areflective surface inside the polarization separating prism 25, and isseparated into rays with three colors (G light, B light, R light)through the TIR prisms 24 a to 24 c. The separated rays with therespective colors are respectively incident into and modulated throughthe corresponding DMD elements 21 a to 21 c, travel through the TIRprisms 24 a to 24 c again in a reverse direction, are subjected to colorsynthesis, are subsequently transmitted through the polarizationseparating prism 25, and are incident into the zoom lens 210. The zoomlens 210 projects an optical image, which is formed by the lightmodulated through the DMD elements 21 a to 21 c, onto a screen 205.

FIG. 9 is a schematic configuration diagram of a projection displaydevice according to still another embodiment of the present invention.The projection display device 300 shown in FIG. 9 has a zoom lens 310according to the embodiment of the present invention, a light source315, reflective display elements 31 a to 31 c as light valvescorresponding to respective color light beams, dichroic mirrors 32 and33 for color separation, a cross dichroic prism 34 for color synthesis,a total reflection mirror 38 for deflecting the optical path, andpolarization separating prisms 35 a to 35 c. In FIG. 9, the zoom lens310 is schematically illustrated. Further, an integrator is disposedbetween the light source 315 and the dichroic mirror 32, butillustration thereof is omitted in FIG. 9.

White light originating from the light source 315 is separated into rayswith three colors (G light, B light, R light) through the dichroicmirrors 32 and 33. The separated rays with the respective colorsrespectively pass through the polarization separating prisms 35 a to 35c, are incident into and modulated through the reflective displayelements 31 a to 31 c respectively corresponding to the rays with therespective colors, are subjected to color synthesis through the crossdichroic prism 34, and are subsequently incident into the zoom lens 310.The zoom lens 310 projects an optical image, which is formed by thelight modulated through the reflective display elements 31 a to 31 c,onto a screen 305.

FIGS. 10 and 11 are external views of a camera 400 which is the imagingapparatus according to the embodiment of the present invention. FIG. 10is a perspective view of the camera 400 viewed from the front side, andFIG. 11 is a perspective view of the camera 400 viewed from the rearside. The camera 400 is a single-lens digital camera on which aninterchangeable lens 48 is detachably mounted and which has no reflexfinder. The interchangeable lens 48 is configured such that a zoom lens49 as the optical system according to the embodiment of the presentinvention is housed in a lens barrel.

The camera 400 comprises a camera body 41, and a shutter button 42 and apower button 43 are provided on an upper surface of the camera body 41.Further, operation sections 44 and 45 and a display section 46 areprovided on a rear surface of the camera body 41. The display section 46is for displaying a captured image or an image within an angle of viewbefore imaging.

An imaging aperture, through which light from an imaging target isincident, is provided at the center on the front surface of the camerabody 41. A mount 47 is provided at a position corresponding to theimaging aperture. The interchangeable lens 48 is mounted on the camerabody 41 with the mount 47 interposed therebetween.

In the camera body 41, there are provided an imaging element, a signalprocessing circuit, a recording medium, and the like. The imagingelement (not shown) such as a charge coupled device (CCD) outputs acaptured image signal based on a subject image which is formed throughthe interchangeable lens 48. The signal processing circuit generates animage through processing of the captured image signal which is outputfrom the imaging element. The recording medium records the generatedimage. The camera 400 captures a still image or a moving image bypressing the shutter button 42, and records image data, which isobtained through imaging, in the recording medium.

The present invention has been hitherto described through embodimentsand examples, but the zoom lens of the present invention is not limitedto the above-mentioned embodiments and examples, and may be modifiedinto various forms. For example, the radius of curvature, the surfacespacing, the refractive index, and the Abbe number of each lens may beappropriately changed.

Further, the projection display device of the present invention is notlimited to that of the above-mentioned configuration. For example, theused light valve and the optical member used in separation or synthesisof rays are not limited to those of the above-mentioned configuration,and may be modified into various forms.

Further, the imaging apparatus of the present invention is also notlimited to the above-mentioned configurations. For example, the presentinvention may be applied to a single-lens reflex camera, a film camera,a video camera, and the like.

EXPLANATION OF REFERENCES

-   -   10, 210, 310: zoom lens    -   11 a to 11 c: transmissive display element    -   12, 13, 32, 33: dichroic mirror    -   14, 34: cross dichroic prism    -   15, 215, 315: light source    -   16 a to 16 c: condenser lens    -   18 a to 18 c, 38: total reflection mirror    -   21 a to 21 c: DMD element    -   24 a to 24 c: TIR prism    -   25, 35 a to 35 c: polarization separating prism    -   31 a to 31 c: reflective display element    -   41: camera body    -   42: shutter button    -   43: power button    -   44, 45: operation section    -   46: display section    -   47: mount    -   48: interchangeable lens    -   49: zoom lens    -   100, 200, 300: projection display device    -   105, 205, 305: screen    -   400: camera    -   G1: first optical system    -   G11: first-1 lens group    -   G12: first-2 lens group    -   G2: second optical system    -   G21: second-1 lens group    -   G22: second-2 lens group    -   G23: second-3 lens group    -   L11 a to L23 a: lens    -   PP: optical member    -   Sim: image display surface    -   St: aperture stop    -   wa: on-axis rays    -   wb: rays with maximum angle of view    -   Z: optical axis

What is claimed is:
 1. A zoom lens configured to form an intermediateimage at a position conjugate to a reduction side imaging plane andconfigured to form the intermediate image again on a magnification sideimaging plane, the zoom lens comprising: a first optical system on themagnification side; and a second optical system on the reduction side,wherein the intermediate image is formed between the magnification sideand the reduction side, wherein the first optical system includes, inorder from the magnification side, a first-1 lens group which haspositive refractive power, and a first-2 lens group which has positiverefractive power, wherein the second optical system includes, in orderfrom the magnification side, a second-1 lens group which has positiverefractive power, a second-2 lens group which has positive refractivepower, and a second-3 lens group which has positive refractive power,wherein the first-2 lens group, the second-1 lens group, and thesecond-2 lens group are configured to be moved by changing spacingsbetween the groups adjacent to each other in a direction of an opticalaxis during zooming, and wherein the first-1 lens group and the second-3lens group are configured to remain stationary with respect to thereduction side imaging plane during zooming.
 2. The zoom lens accordingto claim 1, wherein the following conditional expression (1) issatisfied,5<f12/|fw|<20  (1), where f12 is a focal length of the first-2 lensgroup, and fw is a focal length of the whole system at a wide-angle end.3. The zoom lens according to claim 1, wherein the following conditionalexpression (2) is satisfied,5<f22/|fw|<12  (2), where f22 is a focal length of the second-2 lensgroup, and fw is a focal length of the whole system at a wide-angle end.4. The zoom lens according to claim 1, wherein the following conditionalexpression (3) is satisfied,5<f23/|fw|<12  (3), where f23 is a focal length of the second-3 lensgroup, and fw is a focal length of the whole system at a wide-angle end.5. The zoom lens according to claim 1, wherein during zooming from awide-angle end to a telephoto end, the second-1 lens group is configuredto move from the magnification side to the reduction side, and thesecond-2 lens group is configured to move from the reduction side to themagnification side.
 6. The zoom lens according to claim 1, wherein thefollowing conditional expression (4) is satisfied,−25<f211/|fw|<−2  (4), where f211 is a focal length of a lens closest tothe magnification side in the second-1 lens group, and fw is a focallength of the whole system at a wide-angle end.
 7. The zoom lensaccording to claim 1, wherein the lens closest to the magnification sidein the second-1 lens group is a second-1-1 lens which has negativerefractive power, wherein a lens adjacent to the reduction side of thesecond-1-1 lens is a second-1-2 lens which has positive refractivepower, and wherein the following conditional expression (5) issatisfied,30<ν211−ν212<70  (5), where ν211 is an Abbe number of the second-1-1lens on a basis of a d line, and ν212 is an Abbe number of thesecond-1-2 lens on the basis of the d line.
 8. The zoom lens accordingto claim 1, wherein the following conditional expression (6) issatisfied,2<Bfw/|fw|  (6), where Bfw is a back focal length of the whole system asan air conversion length at a wide-angle end, and fw is a focal lengthof the whole system at the wide-angle end.
 9. The zoom lens according toclaim 2, wherein the following conditional expression (1-1) is satisfied7<f12/|fw|<15  (1-1).
 10. The zoom lens according to claim 3, whereinthe following conditional expression (2-1) is satisfied7<f22/|fw|<10  (2-1).
 11. The zoom lens according to claim 4, whereinthe following conditional expression (3-1) is satisfied6.8<f23/|fw|<10  (3-1).
 12. The zoom lens according to claim 6, whereinthe following conditional expression (4-1) is satisfied−20<f211/|fw|<−3  (4-1).
 13. The zoom lens according to claim 7, whereinthe following conditional expression (5-1) is satisfied34<ν211−ν212<60  (5-1).
 14. The zoom lens according to claim 8, whereinthe following conditional expression (6-1) is satisfied3<Bfw/|fw|<10  (6-1).
 15. A projection display device comprising: alight source; a light valve configured to receive light originating fromthe light source; and the zoom lens according to claim 1, the zoom lensbeing configured to project an optical image onto a screen, the opticalimage being formed when light is modulated through the light valve. 16.An imaging apparatus comprising the zoom lens according to claim 1.